Signs of overpowering

[seicam]

I think this has been discussed on the old forum, but I will ask here again.

I know people typically use the degree of heel on trimaran or that fact that winward ama is flying or leeward ama is burried in water to determine the "overowered" state. What's your rule of thumb? How much is too much?

BTW - Sophia is in the water and looks like we may get the first sail this season on Memorial Day. Hope it will be a good one.

Regards,
Maciek

[Ron]

Maciek -

You've got different types or classes of trimarans. Some, like the America's cup winner, are usually flying 2 hulls, with perhaps 40 degrees of heel as being acceptable. Corsairs are designed to have no more than 2 hulls in the water at any time. One is out of the water even when the boat is stopped. Others, like our Telstars with probably close to a half foot of both amas in the water at the same time, normally don't lift one, or not that much when they do. So degree of heel is sort of meaningless when applied to all of the boats. 20 to 30 degrees of heel on a Corsair 24 may be OK, but I would not like to see that on the significantly heavier Telstar with it's deeper set ama's. I don't think I've ever lifted an ama more than maybe 6 inches out of the water, and that was on a reach in about 22 knots of wind with no reefs. Heel (didn't actually look at gauge) was probably around 10 to 15 percent, boat speed was high 16's.

To me, the key is what's happening to the leeward ama. Bury its bow at a fairly high speed and you could pitch pole. In my example above, there was not that much chop on the bay because of wind direction, so I had no real problems with the bow getting dug in. Heavier chop could lift the windward side and further bury the leeward. The ocean or gulf could have made things worse as well. So there is no real absolute number involved - it's what happening to the leeward ama and under what conditions.

[onremlop]

Having the leeward ama buried also kills your performance and won't make you go any faster. I was out last year with my monohull friends and let them sail my Telstar. I had to interject when we had all the sails up in 25-28 gusts and were burying the leeward amas much to my disgruntlement. Our performance picked up once we reefed in the genny a bit. The monohullers believe that all sailboats will just round up into the wind - I don't find that the case with a multihull.

[simonhayes]

Ron is right, the leeward ama is your guide. I do sail in pretty heavy chop and as that rolls under your beam, you can heel over quite alot, especially if accompanied by a big gust. I don't have a gauge but I am guessing I have seen 35-40 degrees with the windward ama clear out of the water and the leeward ama completely submerged... That is not recommended for the reason Ron indicates and because it is bad for you centerboard ( I have broken 2 of them in less extreme conditions ) but the good news is that it will come back... so you can breathe again and put in a reef pdq... My normal rule of thumb is that, if the aft end of the leeward ama is submerged , it is time to reef..

[Ron]

Simon -

At 35 or 40 degree of heel you're main hull is nearly out of the water as well. That will put well over 4600 pounds (boat + people + stuff) of weight on just the leeward ama pushing it down even more. In that kind of wind and chop I'd probably want to reef a little earlier. Depending on direction, the chop could be slowing you down, but if not - you're doing over 15 knots and become a good candidate for pitch-poling when the ama bow gets stuffed hard.

USA 17 flies nicely at 40 degrees heel, but remember that the boat probably weighs almost nothing (for its size) and the ama's can probably each carry that entire load without washing out. All 3 bow's have extrememly fine entries as well and they have foils under the ama's. You get something for the 30 or 40 million bucks that it probably costs.

[simonhayes]

Ron,

Agreed that that sort of heel in those sort of conditions in not at all advisable. I normally do reef early because the wind can change very fast around here because of the hills . In that case, we went from 16-20 to 30+ almost instantly which what caused the excitement...

[seicam]

Here is my experience from our most recent sail - just writing this to see if it matches yours.

This Saturday we took the boat for a sail. At some point we had wind 13-15knt, with gusts to 16knt (true). We were going close-hauled, with main and full genoa. I could not tell what our speed was, because our knot-meter just got jammed by some seaweed or something (it started working later). But I think it was in range of 6-7 knots, based on the wake wave. For that reason I could not tell the apparent wind as well, but I guess it was approaching 20knt. At that point we had windward ama lifting and maybe just touching the tops of the waves. The leeward ama had the aft end all in water, with ama deck even with the surface. (next time I will just film it). I remembered the advice here, but overall the boat did not feel overpowered and was going fine. The chop was minimal, as this is deep water and we are in fairly protected area. The heel was less than 10 deg.
We decided not to reef as it appeared that the wind will not build up more. In the end, it stayed around 15 knt and dropped a bit later. Overall it was first true day of summer in NW and a great day of sailing.

Let me know if that's similar to what you observe on your boat.

Regards,
Maciek

[Ron]

Maciek -

Hard to tell, wasn't there. The boat speed should have been a little higher considering the wind speed was around 15 knots, but with the loss of the knot meter - maybe it was. I'm assuming you meant that the last 2 feet or so of the leeward ama was in the water and not much else, and that the windward ama was jut starting to lift a drop. It was not really airborn with daylight showing. Sounds just about right. I would not have reefed either. Maybe more wind (20 true) and/or more chop would have gotten me to roll in the genoa 10 percent.

[trashpad]

If Kathy is with me i just keep an eye on her face. it is the best tool around on knowing to reef.

[Dan]

Tony designed the boat to give certain warning signs when it is getting overpowered from my conversations with him. One clear sign is when the leeward ama's aft end stays buried in the water... This is really a boat that sails faster flatter than it does heeled, since it isn't designed to be sailed with an ama flying really. It is a cruising design, designed more for load carrying capacity than sheer speed.